1. Technical Field
Some example embodiments of the present invention generally relate to a sheet processing apparatus, a sheet aligner, and a sheet aligning method for aligning a sheet, for example, a folded sheet.
2. Description of Background Art
A background image forming apparatus, such as a copying machine, a facsimile machine, a printer, or a multifunction printer having copying, printing, scanning, and facsimile functions, forms an image on a recording medium (e.g., a sheet) according to image data. For example, a sheet is sent from a paper tray to an image forming unit. The image forming unit forms an image on the sheet. The sheet bearing the image is output onto an output tray.
When the image forming apparatus forms an image on a large sheet (e.g., an A0 or A1 size sheet) used for drawings, the output tray may not receive the large sheet. If the output tray is large enough to receive the large sheet, then the output tray may be too large to save space. To address this problem, the image forming apparatus is connected to a sheet processing apparatus for folding the large sheet into a small size, folded sheet.
One example of a background sheet processing apparatus includes a jogger fence and a staple fence arranged opposite to each other. When the sheet processing apparatus receives a signal for indicating the size of a sheet to be aligned by the jogger fence and the staple fence from the image forming apparatus, the jogger fence and the staple fence move closer to each other to a standby position so as to be ready for receiving the sheet. At the standby position, a gap of about 10 mm is provided between the jogger fence and an edge of the sheet and between the staple fence and another edge of the sheet. When the jogger fence and the staple fence receive the sheet, the jogger fence further moves toward the staple fence by about 20 mm to align the sheet. Namely, only the jogger fence moves to align the sheet. Therefore, if the sheet is substantially skewed when the jogger fence and the staple fence receive the sheet, the sheet may not be properly aligned.
Another example of a background sheet processing apparatus includes a first folder, a switcher, and a second folder. The switcher includes a sheet guide, an adjuster including a stopper, and a feeder. The second folder includes a folding roller.
The first folder folds a sheet in a first direction. The switcher switches a sheet conveyance direction of the sheet sent from the first folder. Specifically, the sheet guide guides the folded sheet sent from the first folder toward the adjuster. The adjuster performs a registration adjustment on the sheet by causing the sheet to contact the stopper. The feeder feeds the sheet toward the second folder. The second folder folds the sheet in a second direction perpendicular to the first direction.
When the first folder has folded a corner of the head of the sheet, the head of the sheet partially contacts the stopper, resulting in buckling of the sheet. The stopper is not movable. Therefore, when the sheet is conveyed to the second folder, a center line of the sheet in a direction perpendicular to a sheet conveyance direction may vary depending on the type of folding performed by the first folder. Thus, a center of the folding roller in a longitudinal direction of the folding roller may not contact the center line of the sheet in the direction perpendicular to the sheet conveyance direction. When the sheet processing apparatus further includes a tuning device for tuning the sheet folded by the second folder, the sheet may not pivot on the center of the sheet, preventing the turning device from having a compact size.